> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/reference/sql-commands/sql-alterfunction.md).

# ALTER FUNCTION

### ALTER FUNCTION

ALTER FUNCTION — change the definition of a function

### Synopsis

```

ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    action [ ... ] [ RESTRICT ]
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    RENAME TO new_name
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    OWNER TO { new_owner | CURRENT_ROLE | CURRENT_USER | SESSION_USER }
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    SET SCHEMA new_schema
ALTER FUNCTION name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ]
    [ NO ] DEPENDS ON EXTENSION extension_name

where action is one of:

    CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT
    IMMUTABLE | STABLE | VOLATILE
    [ NOT ] LEAKPROOF
    [ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
    PARALLEL { UNSAFE | RESTRICTED | SAFE }
    COST execution_cost
    ROWS result_rows
    SUPPORT support_function
    SET configuration_parameter { TO | = } { value | DEFAULT }
    SET configuration_parameter FROM CURRENT
    RESET configuration_parameter
    RESET ALL
```

### Description

`ALTER FUNCTION` changes the definition of a function.

You must own the function to use `ALTER FUNCTION`. To change a function's schema, you must also have `CREATE` privilege on the new schema. To alter the owner, you must be able to `SET ROLE` to the new owning role, and that role must have `CREATE` privilege on the function's schema. (These restrictions enforce that altering the owner doesn't do anything you couldn't do by dropping and recreating the function. However, a superuser can alter ownership of any function anyway.)

### Parameters

*`name`* : The name (optionally schema-qualified) of an existing function. If no argument list is specified, the name must be unique in its schema.

*`argmode`* : The mode of an argument: `IN`, `OUT`, `INOUT`, or `VARIADIC`. If omitted, the default is `IN`. Note that `ALTER FUNCTION` does not actually pay any attention to `OUT` arguments, since only the input arguments are needed to determine the function's identity. So it is sufficient to list the `IN`, `INOUT`, and `VARIADIC` arguments.

*`argname`* : The name of an argument. Note that `ALTER FUNCTION` does not actually pay any attention to argument names, since only the argument data types are needed to determine the function's identity.

*`argtype`* : The data type(s) of the function's arguments (optionally schema-qualified), if any.

*`new_name`* : The new name of the function.

*`new_owner`* : The new owner of the function. Note that if the function is marked `SECURITY DEFINER`, it will subsequently execute as the new owner.

*`new_schema`* : The new schema for the function.

`DEPENDS ON EXTENSION extension_name`\
`NO DEPENDS ON EXTENSION extension_name` : This form marks the function as dependent on the extension, or no longer dependent on that extension if `NO` is specified. A function that's marked as dependent on an extension is dropped when the extension is dropped, even if `CASCADE` is not specified. A function can depend upon multiple extensions, and will be dropped when any one of those extensions is dropped.

`CALLED ON NULL INPUT`\
`RETURNS NULL ON NULL INPUT`\
`STRICT` : `CALLED ON NULL INPUT` changes the function so that it will be invoked when some or all of its arguments are null. `RETURNS NULL ON NULL INPUT` or `STRICT` changes the function so that it is not invoked if any of its arguments are null; instead, a null result is assumed automatically. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for more information.

`IMMUTABLE`\
`STABLE`\
`VOLATILE` : Change the volatility of the function to the specified setting. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for details.

`[ EXTERNAL ] SECURITY INVOKER`\
`[ EXTERNAL ] SECURITY DEFINER` : Change whether the function is a security definer or not. The key word `EXTERNAL` is ignored for SQL conformance. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for more information about this capability.

`PARALLEL` : Change whether the function is deemed safe for parallelism. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for details.

`LEAKPROOF` : Change whether the function is considered leakproof or not. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for more information about this capability.

`COST` *`execution_cost`* : Change the estimated execution cost of the function. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for more information.

`ROWS` *`result_rows`* : Change the estimated number of rows returned by a set-returning function. See [CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md) for more information.

`SUPPORT` *`support_function`* : Set or change the planner support function to use for this function. See [Section 36.11](/server-programming/extend/xfunc-optimization.md) for details. You must be superuser to use this option.

```
This option cannot be used to remove the support function altogether,
since it must name a new support function. Use `CREATE OR
REPLACE FUNCTION` if you need to do that.
```

*`configuration_parameter`*\
*`value`* : Add or change the assignment to be made to a configuration parameter when the function is called. If *`value`* is `DEFAULT` or, equivalently, `RESET` is used, the function-local setting is removed, so that the function executes with the value present in its environment. Use `RESET ALL` to clear all function-local settings. `SET FROM CURRENT` saves the value of the parameter that is current when `ALTER FUNCTION` is executed as the value to be applied when the function is entered.

```
See [SET](sql-set.md) and
[Chapter 19](../../server-administration/runtime-config/README.md)
for more information about allowed parameter names and values.
```

`RESTRICT` : Ignored for conformance with the SQL standard.

### Examples

To rename the function `sqrt` for type `integer` to `square_root`:

```

ALTER FUNCTION sqrt(integer) RENAME TO square_root;
```

To change the owner of the function `sqrt` for type `integer` to `joe`:

```

ALTER FUNCTION sqrt(integer) OWNER TO joe;
```

To change the schema of the function `sqrt` for type `integer` to `maths`:

```

ALTER FUNCTION sqrt(integer) SET SCHEMA maths;
```

To mark the function `sqrt` for type `integer` as being dependent on the extension `mathlib`:

```

ALTER FUNCTION sqrt(integer) DEPENDS ON EXTENSION mathlib;
```

To adjust the search path that is automatically set for a function:

```

ALTER FUNCTION check_password(text) SET search_path = admin, pg_temp;
```

To disable automatic setting of `search_path` for a function:

```

ALTER FUNCTION check_password(text) RESET search_path;
```

The function will now execute with whatever search path is used by its caller.

### Compatibility

This statement is partially compatible with the `ALTER FUNCTION` statement in the SQL standard. The standard allows more properties of a function to be modified, but does not provide the ability to rename a function, make a function a security definer, attach configuration parameter values to a function, or change the owner, schema, or volatility of a function. The standard also requires the `RESTRICT` key word, which is optional in PostgreSQL.

### See Also

[CREATE FUNCTION](/reference/sql-commands/sql-createfunction.md), [DROP FUNCTION](/reference/sql-commands/sql-dropfunction.md), [ALTER PROCEDURE](/reference/sql-commands/sql-alterprocedure.md), [ALTER ROUTINE](/reference/sql-commands/sql-alterroutine.md)

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/sql-alterfunction.html)（英文原文，待翻譯）


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